In general, such ducting is used for connecting one or more silos to installations such as port installations for loading or unloading the holds of ships.
The ducting is generally built up from interconnected cylindrical tubular elements. Given that these elements are heavy because of their thickness, they are difficult to assemble and replace, particularly when the ducting passes through empty space at great height, making it necessary to use large hoisting means.
Assembly and maintenance work is therefore dangerous and expensive.
In addition, the tubular elements are interconnected by welding. If a worn element is to be replaced, there is a real danger of explosion since the mixture inside the ducting and the silos is explosive, as is well known.
Quite apart from that, the circular cross-section of the ducting is relatively small to enable handling and assembly to be performed without using excessively large means.
As a result the throughput along the ducting is limited, causing ships to be held up for too long a period of time, which is expensive.
Finally, when a leak appears, due to wear since grain is abrasive, the faulty element must be replaced without waiting and as quickly as possible. This presents a real problem of making a tailor-made replacement element and of installing it on site.
The object of the present invention is to remedy these drawbacks:
by proposing a manner of construction whereby the flow cross-section can be considerably increased without requiring exceptional means for assembling or replacing elements;
by replacing welding which is dangerous with a manner of assembly that does not run the risk of explosion and which is easy to implement on site, without danger;
by standardizing the components of the ducting so that they are stockable and can be immediately available; and
by providing means for overcoming the consequences of wear on some of the panels.
U.S. Pat. No. 2 752 950 describes ducting for ventilating and heating purposes in which each length is constituted by four panels, with the top and bottom horizontal panels being plane while the two vertical panels have S-shaped rims protecting inwardly for engaging on the margins of said top horizontal panels. In addition, the rims of the vertical panels are fixed to the margins of the horizontal panels by screws.
This prior art ducting is not subject to the risk of explosion, nor is it subject to the constraints of ducting repair as is the ducting of the present application, and as a result it suffers from numerous drawbacks.
In particular, the panel fixing means are only partially accessible, thereby making disassembly difficult, and if the fixing means jam they must be destroyed which may damage the panels. In addition, the disassembly of one panel is necessarily accompanied by at least partial disassembly of adjacent panels. Further, sealing at the junction between panels in a given length and between panels in contiguous lengths is not provided to satisfactory safety standards applicable to ducting for transporting grains or other substances. Above all, no means are described or suggested for countering the risk of wear.
While aiming for the above-mentioned object, the present invention naturally seeks to remedy these drawbacks of the prior art ducting insofar as it implements the combination of means used in the ducting taught by U.S. Pat. No. 2 752 950, whereby an elementary length of the ducting is constituted by four independent panels comprising an opposite pair of panels which are plane and two other panels having rims applied against the margins of the plane panels and predrilled as are said margins in order to pass fixing means passing from the outside through the margins and the rims after they have been put into contact.